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Groups > comp.arch.embedded > #13150 > unrolled thread
| Started by | Luis Filipe Rossi <luisf.rossi@gmail.com> |
|---|---|
| First post | 2013-08-22 10:33 -0700 |
| Last post | 2013-08-27 12:49 -0400 |
| Articles | 5 on this page of 25 — 12 participants |
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Routing signals under crystals Luis Filipe Rossi <luisf.rossi@gmail.com> - 2013-08-22 10:33 -0700
Re: Routing signals under crystals Tim Wescott <tim@seemywebsite.really> - 2013-08-22 16:25 -0500
Re: Routing signals under crystals upsidedown@downunder.com - 2013-08-23 09:35 +0300
Re: Routing signals under crystals Tim Wescott <tim@seemywebsite.really> - 2013-08-23 12:43 -0500
Re: Routing signals under crystals Richard Damon <Richard@Damon-Family.org> - 2013-08-22 21:45 -0400
Re: Routing signals under crystals MK <mk@nospam.co.uk> - 2013-08-23 08:40 +0100
Re: Routing signals under crystals Mike Perkins <spam@spam.com> - 2013-08-23 11:05 +0100
Re: Routing signals under crystals Luis Filipe Rossi <luisf.rossi@gmail.com> - 2013-08-23 04:55 -0700
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-23 16:10 -0400
Re: Routing signals under crystals Clifford Heath <no.spam@please.net> - 2013-08-24 09:55 +1000
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-23 20:23 -0400
Re: Routing signals under crystals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-24 09:41 +0100
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-24 12:10 -0400
Re: Routing signals under crystals Tom Gardner <spamjunk@blueyonder.co.uk> - 2013-08-24 17:21 +0100
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-24 12:53 -0400
Re: Routing signals under crystals Clifford Heath <no.spam@please.net> - 2013-08-24 23:11 +1000
Re: Routing signals under crystals Don Y <this@isnotme.com> - 2013-08-23 19:43 -0700
Re: Routing signals under crystals Richard Damon <Richard@Damon-Family.org> - 2013-08-24 00:34 -0400
Re: Routing signals under crystals Mark Borgerson <mborgerson@comcast.net> - 2013-08-23 22:16 -0700
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-24 12:19 -0400
Re: Routing signals under crystals Mark Borgerson <mborgerson@comcast.net> - 2013-08-24 09:59 -0700
Re: Routing signals under crystals Randy Yates <yates@digitalsignallabs.com> - 2013-08-24 22:27 -0400
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-25 16:20 -0400
Re: Routing signals under crystals Randy Yates <yates@digitalsignallabs.com> - 2013-08-25 21:04 -0400
Re: Routing signals under crystals rickman <gnuarm@gmail.com> - 2013-08-27 12:49 -0400
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| From | Mark Borgerson <mborgerson@comcast.net> |
|---|---|
| Date | 2013-08-24 09:59 -0700 |
| Message-ID | <MPG.2c8286544328807b9896bb@news.eternal-september.org> |
| In reply to | #13184 |
In article <kvame9$tg8$1@dont-email.me>, gnuarm@gmail.com says... > > On 8/24/2013 1:16 AM, Mark Borgerson wrote: > > > > I agree with that. It's probably even less of a problem when the > > fastest clock on the board is in the internal processor of the > > SD card logging the data. Writing to an SD card can generate quite > > a burst of EMI, but I haven't seen large effects on crystal behavior. > > Really? I've never seen significant EMI directly generated by any chip. > The problem is normally the power distribution to the chip giving off > the EMI. Is that what you are talking about, the power distribution to > the SD card? Or does this come directly from the card itself? I > suppose the PSD on the SD card might not be up to snuff. I think you're correct in that the EMI occurs on the power supply lines, rather than in the chip itself. I've taken the usual steps---decoupling to the ground plane etc. I've also used a separate linear regulator for the SD card power. When writing, the SD card seems to draw >50mA for microseconds at a time---it's difficult to tell exactly as the bandwidth of my current sensor isn't that high and the current pulses are (I hope) modified by the regulator and bypass capacitors. I wonder if the noise relates directly to the current demands of the flash memory's charge pump that generates the programming voltage. When I get time, I'll take my RF sniffer (an old portable radio) and see if there's a significant difference in EMI between reads and writes. Mark Borgerson
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| From | Randy Yates <yates@digitalsignallabs.com> |
|---|---|
| Date | 2013-08-24 22:27 -0400 |
| Message-ID | <87a9k6wlmn.fsf@digitalsignallabs.com> |
| In reply to | #13184 |
rickman <gnuarm@gmail.com> writes: > On 8/24/2013 1:16 AM, Mark Borgerson wrote: >> >> I agree with that. It's probably even less of a problem when the >> fastest clock on the board is in the internal processor of the >> SD card logging the data. Writing to an SD card can generate quite >> a burst of EMI, but I haven't seen large effects on crystal behavior. > > Really? I've never seen significant EMI directly generated by any > chip. How do you know where it's coming from? Do you have screen rooms, antennae, spectrum analyzers, etc., like FCC testing centers do? -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2013-08-25 16:20 -0400 |
| Message-ID | <kvdove$5v5$1@dont-email.me> |
| In reply to | #13188 |
On 8/24/2013 10:27 PM, Randy Yates wrote: > rickman<gnuarm@gmail.com> writes: > >> On 8/24/2013 1:16 AM, Mark Borgerson wrote: >>> >>> I agree with that. It's probably even less of a problem when the >>> fastest clock on the board is in the internal processor of the >>> SD card logging the data. Writing to an SD card can generate quite >>> a burst of EMI, but I haven't seen large effects on crystal behavior. >> >> Really? I've never seen significant EMI directly generated by any >> chip. > > How do you know where it's coming from? Do you have screen rooms, > antennae, spectrum analyzers, etc., like FCC testing centers do? Lol, if you have EMI, you fix the board and it goes away, that shows it wasn't the chip... Same with the SD card. Replace the SD card with a different brand and the EMI should change or go away. -- Rick
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| From | Randy Yates <yates@digitalsignallabs.com> |
|---|---|
| Date | 2013-08-25 21:04 -0400 |
| Message-ID | <87sixxtg8o.fsf@digitalsignallabs.com> |
| In reply to | #13189 |
rickman <gnuarm@gmail.com> writes: > On 8/24/2013 10:27 PM, Randy Yates wrote: >> rickman<gnuarm@gmail.com> writes: >> >>> On 8/24/2013 1:16 AM, Mark Borgerson wrote: >>>> >>>> I agree with that. It's probably even less of a problem when the >>>> fastest clock on the board is in the internal processor of the >>>> SD card logging the data. Writing to an SD card can generate quite >>>> a burst of EMI, but I haven't seen large effects on crystal behavior. >>> >>> Really? I've never seen significant EMI directly generated by any >>> chip. >> >> How do you know where it's coming from? Do you have screen rooms, >> antennae, spectrum analyzers, etc., like FCC testing centers do? > > Lol, if you have EMI, you fix the board and it goes away, that shows > it wasn't the chip... Same with the SD card. Replace the SD card > with a different brand and the EMI should change or go away. Sure. But remember all those funny interactions you were talking about? -- Randy Yates Digital Signal Labs http://www.digitalsignallabs.com
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| From | rickman <gnuarm@gmail.com> |
|---|---|
| Date | 2013-08-27 12:49 -0400 |
| Message-ID | <kvilb4$7v5$1@dont-email.me> |
| In reply to | #13190 |
On 8/25/2013 9:04 PM, Randy Yates wrote: > rickman<gnuarm@gmail.com> writes: > >> On 8/24/2013 10:27 PM, Randy Yates wrote: >>> rickman<gnuarm@gmail.com> writes: >>> >>>> On 8/24/2013 1:16 AM, Mark Borgerson wrote: >>>>> >>>>> I agree with that. It's probably even less of a problem when the >>>>> fastest clock on the board is in the internal processor of the >>>>> SD card logging the data. Writing to an SD card can generate quite >>>>> a burst of EMI, but I haven't seen large effects on crystal behavior. >>>> >>>> Really? I've never seen significant EMI directly generated by any >>>> chip. >>> >>> How do you know where it's coming from? Do you have screen rooms, >>> antennae, spectrum analyzers, etc., like FCC testing centers do? >> >> Lol, if you have EMI, you fix the board and it goes away, that shows >> it wasn't the chip... Same with the SD card. Replace the SD card >> with a different brand and the EMI should change or go away. > > Sure. But remember all those funny interactions you were talking about? No, I don't. The point is that if the chip were faulty you would not be able to fix it in the board. If you can design a board that limits the EMI of the design, then by definition the problem is not the chip. Are you suggesting that the board could be designed in a way that it creates EMI that emanates from the chip? My point is that the chip or SD card can be used in a design so that doesn't generate EMI or the chip generates EMI no matter what you do. I don't really care what ends up being the antenna because that is a pointless distinction. -- Rick
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